High pressure areas are labeled "H". High-pressure areas form due to downward motion through the troposphere, the atmospheric layer where weather occurs. Preferred areas within a synoptic flow pattern in higher levels of the troposphere are beneath the western side of troughs., High-pressure systems bring fair weather, clear skies, and calm air. Low-pressure systems bring unstable air, clouds, and precipitation – ranging from light drizzle to heavy storms. Now, let’s explore each pressure system in detail., When you see a rising barometer, expect fewer clouds, calm winds, and clear skies. High-pressure zones are marked with a blue 'H' on weather maps to show higher air pressure. Learning to forecast the weather means understanding the type of weather associated with an approaching high-pressure zone., Weather prediction: Expect fair, dry, cool weather and a strong breeze. The daily total fluctuation in pressure in Ashburn is 3.4 hPa, with a low of 1006.5 hPa and a high of 1009.9 hPa. Show 2 days, 7 days, or 14 days chart. Track the barometric pressure in Ashburn hour by hour and stay informed about how it will change over the next 6 hours., On weather maps, a low pressure system is labeled with red L. A high pressure system has higher pressure at its center than the areas around it. Winds blow away from high pressure., .